Friday, 28 June 2013

Horses from the permafrost and beyond

Remarkably it has proven possible to sequence the genome of a Middle Pleistocene horse from a bone preserved for 700,000 years in the Canadian permafrost (summary and links here). Comparison with the genomes of modern horses and a more recent fossil yielded several interesting results. Among them, Przewalski's horse was shown to be a wild subspecies uncontaminated by domestic breeds.

Przewalski's horse was once listed as extinct in the wild but a successful captive breeding and release program has changed its status to endangered. There are several images of the placenta of Przewalski's horse on Benirschke's web site (see previous post). The equine placenta is epitheliochorial and has microcotyledons as pictured above.

Soft tissues usually are not preserved for posterity but a putative placenta accompanies a Middle Eocene fossil of the equid genus Propalaeotherium (cited here).